Praziquantel, also referred to as Biltricide, is a broad-spectrum anti-parasitic medicament. It has a broad helminthic spectrum, and works on killing Schistosoma japonica, Schistosoma haematobia, Schistosoma mansoni and the like. Moreover, it also works on killing Paragonimus (Paragonimus westermani), Clonorchis endemicus, hydatid, cysticercus, Sparganum mansoni, Fasciolopsis buski, cestode, etc. Praziquantel is provided with characteristics of high efficacy, short treatment period, low dosage, fast metabolism, low toxicity and convenience for oral administration. The discovery of praziquantel brought a significant breakthrough in the parasistic chemotherapy, which has now become the drug of choice for treating various helminthiasis.
Praziquantel was first synthesized by Seubert, et al. in 1975, and two German pharmaceutical companies, E-Merck and Bayer successfully developed this medicament. It was first brought to market by E-Merck, Inc., with a trade name of Cesol in 1980, and has now been widely used in the world. Besides human use, it is also used for anti-parasitic treatment in animals, fowls, etc. However, toxic and harmful compounds (substances or reagents), such as potassium cyanide, cyclohexanoyl sulphoxide chloride and so forth, are required during the conventional preparation of praziquantel which also requires a long process route and harsh experimental conditions.

Recently, optical isomers of R-praziquantel and S-praziquantel were obtained through resolution of racemic praziquantel by Chinese researchers and discoveries were made from preclinical and early clinical trials that R-praziquantel is the active component of praziquantel against worms, and S-praziquantel is an inactive and even deleterious component; R-praziquantel provides better clinical efficacy than praziquantel at the same dose. Although the World Health Organization has been expecting to develop R-praziquantel to replace praziquantel, the technical problem of low yield in the chemical synthesis of R-praziquantel has been a pending issue for years, see the synthesis scheme above.